Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description adds meaningful behavioral context beyond the annotations: the tool returns a presigned URL rather than uploading directly, requires the caller to PUT file bytes, and depends on storage host reachability. It also states the follow-up step of passing the URL into create_post, which is valuable context the annotations do not provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three sentences with each one earning its place: the primary use case, the exact upload workflow, and the fallback alternative. It is front-loaded with the key decision and contains no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For this tool, the description is functionally complete: it tells the agent what the tool returns, what to do with that return value, and when to choose a different tool. The two required parameters are simple enough that schema validation covers them, and no output schema exists to require return-value documentation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema provides no descriptions and the description does not explicitly explain the filename and contentType parameters. The parameter names are somewhat self-explanatory, but there is no detail on expected formats, MIME types, or naming constraints. With 0% schema coverage, the description should have compensated with at least brief parameter guidance.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly identifies the tool's function: obtain a presigned URL for uploading media via HTTP PUT. It distinguishes this from upload_media by explicitly labeling it the preferred path when HTTP PUT is possible, so an agent can immediately tell the two siblings apart.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage guidance is explicit: use this tool when your runtime can HTTP PUT, then PUT the file bytes and pass the returned public URL to create_post. It also names the fallback alternative, upload_media, when the storage host is unreachable, which fully covers the when-to-use decision.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.